linux-kernel - Re: [bug, 2.6.26-rc4/rc5] sporadic bootup crashes in blk_lookup_devt()/prepare

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20080609191521.1a56b6a6@gondolin.boeblingen.de.ibm.com>
Date:	Mon, 9 Jun 2008 19:15:21 +0200
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Vegard Nossum <vegard.nossum@...il.com>,
	Adrian Bunk <bunk@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jens Axboe <jens.axboe@...cle.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Kay Sievers <kay.sievers@...y.org>, Neil Brown <neilb@...e.de>,
	Mariusz Kozlowski <m.kozlowski@...land.pl>,
	Dave Young <hidave.darkstar@...il.com>
Subject: Re: [bug, 2.6.26-rc4/rc5] sporadic bootup crashes in
 blk_lookup_devt()/prepare_namespace()

On Mon, 9 Jun 2008 09:15:40 -0700 (PDT),
Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> And this is all still ignoring the locking issue, of course. It would be 
> trivial to just remove the block_class_lock, and change
> 
> 	mutex_[un]lock(&block_class_lock);
> 
> into
> 
> 	down|up(&block_class.sem);
> 
> except for _one_ case, which is
> 
> 	bdev_map = kobj_map_init(base_probe, &block_class_lock);
> 
> which really wants a mutex, not a sempahore.
> 
> So to fix that, we'd need to make the class->sem be a mutex, and pass that 
> in. Which is probably a good change too, but makes the whole thing much 
> bigger.

The driver core changes in -next convert class->sem to
class->p->class_mutex, which makes it non-accessible to drivers.
Most of the locking is easily done through converting to the class
iterator functions, but there are some cases where this is not going to
work:

- The {register,unregister}_blkdev() functions, which don't directly
involve the class.
- The iterators for /proc/partitions, which take the lock in
part_start() and give it up again in part_stop().

Maybe we need a possibilty for a driver to lock a class from outside?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/